Trapped under ice with no oxygen for months, goldfish turn to booze. And can you blame 'em?

Carp diem, indeed

Scientists have discovered how goldfish and their wild ilk survive months of winter in frozen-over lakes of oxygen-free water. The answer is alcohol – the cause of, and solution to, all of life's problems.

There aren't many vertebrates that can survive without oxygen. However, goldfish, and their wild relatives, the crucian carp, share a genetic mutation that allows them to anaerobically convert excess lactic acid into ethanol and flush it out of their gills. The fish are thought to be the only known vertebrates with this talent – the more's the pity.

"During their time in oxygen-free water in ice-covered ponds, which can last for several months in their northern European habitat, blood alcohol concentrations in crucian carp can reach more than 50 mg per 100 milliliters, which is above the drink drive limit in these countries," said Dr Michael Berenbrink, an evolutionary physiologist at the University of Liverpool in the UK, on Friday.

"However, this is still a much better situation than filling up with lactic acid, which is the metabolic end product for other vertebrates, including humans, when devoid of oxygen."

This insanely useful skill comes down to the fish having two different sets of proteins in their muscles for breaking down carbohydrates – one similar to our own and a second, unique protein that allows them to produce ethanol. The research has been published in the journal Scientific Reports.

"The ethanol production allows the crucian carp to be the only fish species surviving and exploiting these harsh environments, thereby avoiding competition and escaping predation by other fish species with which they normally interact in better oxygenated waters," said Dr Cathrine Elisabeth Fagernes, from the University of Oslo, in Norway.

"It's no wonder then that the crucian carp's cousin the goldfish is arguably one of the most resilient pets under human care."

For those of you reading this after a boozy night on the town be warned – putting your goldfish in the freezer and then sucking it isn't going to get you more drunk, so don’t try it. ®